Welcome!
Unfortunately, there is no longer an electronic way to give Apple feedback—good or bad—regarding sales, service or support experiences with their employees. All that is left are product-specific feedback links and I doubt that will get get your kind comments to the right people.
IMHO, this is best handled—and most beneficial to the Support person your encountered—with a proper business letter to Apple HQ:
Phone calls only generate pink "While you were out..." slips or lots of voicemails that give no one joy first thing in the morning. Been there, done that!
A letter gives supervisors time to review and take action. I used to manage the customer support functions for a large consumer product corporation in another sector. I preferred letters regarding employee action by a couple of orders of magnitude over phone calls. Letter become documentation for the employees' personnel files, and very useful at review time. The letter give the highest chance of your kindness in saying "thank you" helping the person who kindly helped you.
If you had a case number, include that. It may be the only way Apple can link your good experience to a particular person.
AJ
PS: I understand that writing business letters is not taught like it was when I when to school with dinosaurs. If you need a brush-up, this outside article is quite good:
https://edu.gcfglobal.org/en/business-communication/how-to-write-a-formal-business-letter/1/
